Abstract—This report presents the results of an experiment aimed at observation of the muon catalyzed 3Hed fusion reaction 3He + μ d → ^3Heμ d → ^4He (3.66 MeV) + p (14.64 MeV) + μ which might occur after a negative muon stop in the D2 + 3He gas mixture. The basic element of the experimental setup is a Time Projection Chamber (TPC) which can detect the incoming muons and the products of the fusion reaction. The TPC operated with the D2 + 3He (5 10^8 3Heμd molecules were produced with only 2 registered candidates for the muon catalyzed 3Hed fusion with the expected background N_bg = 2.2 ± 0.3 events. This gives an upper limit for the probability of the fusion decay of the 3Heμd molecule P_F(^3Heμ d) ⩽ 1.1 ×10^ - 7 at 90 λ_d^3He = 192(3) ×10^6 s^ - 1 and the probability of the fast muon transfer from the excited to the ground state of the μ d atom q_1S = 0.80(3) . The obtained results are compared with the previously published data.

The nuclear dd-fusion reaction can proceed by three possible channels: ^3H+p (≈ 50%) , ^3He+n (≈ 50%) , ^4He+γ (≈ 10^-7%) . Interest in dd-fusion has been aroused by both fundamental research and astrophysics and applied science, particularly in the field of fusion reactor development. In the 1970s, the idea of studying the nuclear dd-fusion reaction using polarized deuteron beams was proposed at the Kurchatov Institute. The development of this idea was continued in the PolFusion (polarized fusion) nuclear physics experiment, which aims at studying the reaction of nuclear dd synthesis with polarized source particles in the low energy region. The experiment is planned to measured the scattering asymmetries of dd-fusion reaction products in the final state at different mutual orientation of the spins of colliding deuterons in the energy range 10–100 keV. The authors present an overview of the status of the experiment.

Available data on the polarization of the secondary proton (as a function of its momentum K) in the inelastic (p, p') reactions with the ^9Be, ^12C, and ^40Ca nuclei and differential cross section data (the momentum distributions) for the reactions at the initial proton energy 1 GeV and scattering angles Θ=21^∘ and Θ=24.5^∘ were analysed in a range of the high momenta K close to the momentum corresponding to the proton elastic scattering off the investigated nucleus. A structure in the polarization and momentum distribution data at the high momenum K, related probably to quasi-elastic scattering off a ^8Be-like nucleon cluster inside the nuclei, was observed.

The secondary proton polarization and differential cross sections of the ($$p,p^{\prime}$$) inelastic reaction on nuclei $${}^{9}$$Be and $${}^{90}$$Zr at the initial proton energy of 1 GeV were measured over a wide range of the scattered proton momenta at a laboratory angle of $$\Theta=21^{\circ}$$. Scattered protons were detected by means of the magnetic spectrometer equipped with a polarimeter based on multiwire proportional chambers and carbon analyzer. A structure in the polarization and cross section data, related probably to the quasielastic scattering off nucleon correlations in the $${}^{9}$$Be and $${}^{90}$$Zr nuclei, was observed as earlier in the same data for the $${}^{12}$$C, $${}^{28}$$Si, $${}^{40}$$Ca and $${}^{56}$$Fe nuclei. A difference in the momentum distributions of the scattering cross section ratios for the $${}^{90}$$Zr and $${}^{12}$$C nuclei and for the $${}^{90}$$Zr and $${}^{9}$$Be nuclei was observed.

The possibility to exploit spin physics in fusion science opens new impressive panorama and challenging fields to be explored. In addition to the fundamental interesting topics the PREFER collaboration is trying with synergetic efforts to make the well known behaviour of spin–dependent nuclear reactions available for feasability studies and experimental tests for fusion programs. In this contribution the main challenges of the different collaborating groups will be put in evidence, and recent developments with the respective references will be provided.

The secondary proton polarization, differential cross section, and cross section ratios were measured in the (p, p') inelastic reaction with nuclei at 1 GeV and a laboratory scattering angle of Theta = 21 degrees. The data were obtained over a wide range of the scattered proton momentum covering the pN quasielastic peak and high momentum region up to a momentum corresponding to excited level of the nucleus under investigation. Scattered protons were detected by the magnetic spectrometer equipped with a polarimeter based on multiwire proportional chambers and carbon analyzer. A structure in the polarization and cross section data, possibly related to the in-medium elastic scattering on nucleon correlations arising in nuclei, and a scaling of the scattering cross section ratios of the nuclei were observed in the high momentum range.

The secondary-proton polarization and differential cross sections for the ( p, p' ) inelastic reaction on 28 Si and 56 Fe nuclei at the initial proton energy of 1 GeV were measured over a wide range of the scattered-proton momenta at a laboratory angle of Θ = 21◦. Scattered protons were detected by means of a magnetic spectrometer equipped with a polarimeter based on multiwire proportional chambers and a carbon analyzer. A structure in the polarization and cross section data, which is probably related to quasielastic scattering off nucleon correlations in the 28 Si and 56 Fe nuclei, was observed as earlier in the analogous data for 12 C and 40 Ca nuclei. Momentum intervals within which cross-section ratios for nuclei did not depend on the scattered-proton momentum were found.

The differential cross sections of the ( p, p ′) inelastic reaction on nuclei 12 C, 28 Si, 40 Ca, and 56 Fe at the initial proton energy of 1 GeV were measured over a wide range of the scattered proton momenta at a laboratory angle of Θ = 21°. Scattered protons were detected by means of the magnetic spectrometer equipped with a polarimeter based on multiwire proportional chambers. Momentum intervals were observed in which the ratios of the scattering cross sections off the nuclei do not depend on the scattered proton momentum (i.e., scaling).

The polarization of secondary protons in the (p, p’) inelastic reactions on 40Ca and 12C nuclei at the initial proton energy of 1 GeV was measured over a wide range of scattered-proton momenta at a laboratory angle of Θ = 21°. The reaction cross sections were also measured. Scattered protons were detected by means of magnetic spectrometer equipped with a polarimeter based on multiwire-proportional chambers. A structure in the polarization and cross-section data, which is probably related to scattering off nucleon correlations in the nuclei involved, was observed.

The polarization of the secondary protons in the inelastic (p, p') reaction on the 40Ca nucleus at the initial proton energy 1 GeV was measured in a wide range of the scattered proton momenta at a laboratory angle Θ = 21°. The final protons from the reaction have been detected using the magnetic spectrometer equipped with multiwire-proportional chambers polarimeter. A structure of the polarization data, related probably to scattering off the nucleon correlations in the nucleus, has been observed.

The HERMES experiment at DESY studies the spin structure of hadrons. In the experiment, the 27.6 GeV longitudinally polarized positron beam of the HERA e-p collider is passed through an open-ended tubular storage cell in which polarized (longitudinally or transversely) or unpolarized target atoms in undiluted gaseous form are continuously injected. An average beam polarization is typically 55%. The beam helicity is reversed every month during the period of data taking. The target polarization is about 90%, being reversed every 90 seconds. The secondary particles are detected with a large acceptance forward spectrometer described in details in paper of K. Ackerstaff et al., Nucl. Instr. Meth. A 417, 230 (1998). Briefly, the HERMES spectrometer consists of multiple tracking stages before and after a 1.3 T⋅m dipole magnet. Electrons and positrons are identified by the combination of a lead-glass calorimeter, a scintillation hodoscope preceded by two radiation lengths of lead (the pre-shower detector), and a transition-radiation detector (TRD). A Ring-Imaging Cherenkov detector (RICH) allows separation of pions, kaons and protons. Due to reliable particle identification and relatively large acceptance the HERMES experiment measures not only inclusive reactions in deep-inelastic scattering (DIS), where only the scattered lepton is detected, but also semi-inclusive DIS events (SIDIS), where hadrons are detected in coincidence with the lepton. The HERMES experiment started data taking in the year 1995. By the end of 2006, 7.5 × 10 inclusive DIS events (with Q > 1 GeV where Q is the negative four-momentum transfer squared for virtual photon) were accumulated at the integrated luminosity of 1505 pb. Most of the data were collected from the hydrogen and deuterium targets but in order to study nuclear effects the He, N, Ne and Kr targets were also used. The polarized target data amount about 1/4 of the whole HERMES data set. The PNPI is involved in the HERMES since its design phase with a substantial contribution to the hardware and software of the experiment, spectrometer maintenance and data analysis. In this paper selected analysis topics, in which PNPI plays a leading (or significant) role, are presented.

An experimental method to measure the parity non-conserving (PNC) nuclear-spin-dependent amplitudes in transitions between hyperfine sublevels of the ground state of potassium is considered. The principal contribution to the PNC amplitude comes from the nuclear anapole moment. The shotnoise-limited sensitivity to the PNC amplitude is estimated to be » 1% with about an hour of data accumulation time. Possible systematic effects are analyzed and methods to eliminate them are discussed. A precision measurement of the nuclear-spin-dependent amplitude may also permit to search for new physics beyond the Standard Model. Ïðåïðèíò N 2275, 9.12.1998ã. E-mail: vryabov@hep486.pnpi.spb.ru Study of Polarization in Quasi-Elastic (p, 2p) Reactions on Nuclei 6Li, 7Li, 28Si in Complete Kinematics at 1 GeV O. V. Miklukho, N. P. Aleshin, S. L. Belostotski, O. A. Domchenkov, Yu. V. Dotsenko, Yu. V. Elkin, O. G. Grebenyuk, O. Ya. Fedorov, A. A. Izotov, A. A. Jgoun, A. Yu. Kiselev, E. N. Komarov, P. V. Kravchenko, M. P. Levchenko, Yu. G. Naryshkin, V. V. Nelyubin, V. N. Nikulin, A. N. Prokofiev, D. A. Prokofiev, Yu. A. Scheglov, A. V. Shvedchikov, V. V. Vikhrov, A. A. Zhdanov